In recent years there has been a dramatic increase in the number of therapeutic peptides and proteins that have been approved for use or are in advanced clinical trails (Walsh, Nat. Biotechnol. (2006), 24, 769-776; Kumar et al., Curr. Pharm. Biotechnol. (2006), 7, 261-276; Jarvis et al., Chem. Eng. News (2009), 87, 28-29). Methods for their delivery are still primarily based on injectable formulations, often with inconvenient dosing regimes (Walsh, Nat. Biotechnol. (2006), 24, 769-776). For example, an important barrier to the ideal management of diabetes is a complex regimen of injections for insulin delivery, combining constant background (basal) release of insulin and increased dosages (bolus) after meals.
Accordingly, there is a need to provide a more convenient, less intrusive method of administering such therapeutic agents to patients, for example in the form of a molecular reservoir from which the therapeutic agent may be released as needed.